I want to install a sink. There is a buried water line (1" poly) to the site of the sink, with a nice long tail on it if needed. The faucet from an old-fashioned separate faucet system, with one input only, at 1/2" thread.

Note that this is cold water only, just for an easy place to wash hands.

Later I may want to add other fixtures. No specific plans, but it might be nice to be able to do so without digging up the water line again. I guess this means I shouldn't reduce to a minimum size with an underground fitting.

It's about 5' from the faucet to the buried pipe.

One option is to bend the 1" poly line and bring it right up to the faucets. I guess I'd need a barbed insert to 3/4" threaded fitting + a 3/4" to 1/2" reducer. Underground I used brass fittings, so I don't have to worry about steel rusting or whatever, but for this situation, should I save the money and get steel? Or PVC? Or nylon?

One option is to put a 90 degree brass elbow in the ground to a riser of some other material (PEX? PVC? Copper?) that comes up below the sink. There are multiple options for how that riser connects to the sink.

I'm used to sinks having a flexible braided hose between the shutoff and the faucet; is that important, or could a rigid riser connect straight to the faucet?

A shutoff valve below the sink might be a good idea, so I don't have to turn off the upstream valve to work on it.

EDIT: I bought a PVC 1" barbed to 1/2" threaded fitting and a kit with a 2' braided hose and a shutoff valve. So I'll try bringing the 1" poly up to under the sink, and then use these bits. We'll see...

2 Answers
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EDIT: I bought a PVC 1" barbed to 1/2" threaded fitting and a kit with a 2' >braided hose and a shutoff valve. So I'll try bringing the 1" poly up to under the >sink, and then use these bits. We'll see...

I would have probably done that as well (caveat: I am only vaguely familiar with poly, aka "Polybutylene." I have never used it for a job or even had to replace it...It's very uncommon here in northeast Ohio. ) although at first thought, I'm not sure whether it makes a difference to put the Poly to PVC underground or above. I'd also probably put that poly above the sink, then put the Poly to PVC fitting > then the shut off valve, and finally, the braided hose to the faucet..

Underground or not really depends on the material. In this case, I'd have the poly come above ground and make the connections there. You want to minimize buried connections, and poly is fine to have underground. It also gives you more flexibility: you have access to the 1" line to T off from, rather than a 1/2" line. And as you say you're using braided hose: that is definitely not suitable for underground connections or use.

With poly, the best materials in my opinion are PVC and brass. With steel you'll get galvanic corrosion if it is touching any other metal (such as a copper line connected to it), and I personally just don't think steel stands up over time, I've seen too many rusted steel parts (even with galvanized steel, the threads often rust). Nylon is cheap, but it's soft - when something is really tight, you're more likely to end up with a stripped fitting than disconnecting it.

You should have the PVC or brass barb in the poly, put in by heating up the poly a bit with a torch (MAPP, or propane in a pinch), and clamped with one or two gear clamps. Then you can put whatever fittings on top to get to your sink -- as you've said, the braided hose is perfect.